Use GUID to generate unique temp file names and retire GetTempFileName

base/files/file_util_win.cc

Index: base/files/file_util_win.cc
diff --git a/base/files/file_util_win.cc b/base/files/file_util_win.cc
index 65dc5ce1e2fe7495624cc6d8c16b954395eb11ac..f057d14037367bd56d7570908187e93e99a96132 100644
--- a/base/files/file_util_win.cc
+++ b/base/files/file_util_win.cc
@@ -20,6 +20,7 @@
 
 #include "base/files/file_enumerator.h"
 #include "base/files/file_path.h"
+#include "base/guid.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/metrics/histogram.h"
@@ -340,19 +341,26 @@ FILE* CreateAndOpenTemporaryFileInDir(const FilePath& dir, FilePath* path) {
 bool CreateTemporaryFileInDir(const FilePath& dir, FilePath* temp_file) {
   ThreadRestrictions::AssertIOAllowed();
 
-  wchar_t temp_name[MAX_PATH + 1];
-
-  if (!GetTempFileName(dir.value().c_str(), L"", 0, temp_name)) {
+  FilePath::StringType temp_file_name =

[grt (UTC plus 2), 2017/04/06 10:35:02]

please leave a comment explaining why GetTempFileName isn't used -- we wouldn't
want someone to come along a year from now and switch back without realizing why
we're switching away. :-)

[chengx, 2017/04/06 17:46:01]

Comments added.

+      ASCIIToUTF16(base::GenerateGUID() + ".tmp");
+  FilePath temp_name = dir.Append(temp_file_name);
+  File file(::CreateFile(temp_name.value().c_str(),

[grt (UTC plus 2), 2017/04/06 10:35:02]

can you not use the (const FilePath& path, uint32_t flags) ctor of base::File?

[chengx, 2017/04/06 17:46:01]

Done. Changed to the (const FilePath& path, uint32_t flags) ctor.

+                         GENERIC_READ | GENERIC_WRITE,
+                         FILE_SHARE_READ | FILE_SHARE_WRITE, nullptr,
+                         CREATE_NEW, FILE_ATTRIBUTE_NORMAL, nullptr));
+  if (!file.IsValid()) {
     DPLOG(WARNING) << "Failed to get temporary file name in "
                    << UTF16ToUTF8(dir.value());
     return false;
   }
+  file.Close();
 
   wchar_t long_temp_name[MAX_PATH + 1];
-  DWORD long_name_len = GetLongPathName(temp_name, long_temp_name, MAX_PATH);
+  DWORD long_name_len =
+      GetLongPathName(temp_name.value().c_str(), long_temp_name, MAX_PATH);
   if (long_name_len > MAX_PATH || long_name_len == 0) {
     // GetLongPathName() failed, but we still have a temporary file.
-    *temp_file = FilePath(temp_name);
+    *temp_file = temp_name;
     return true;
   }